CamTwistfor Mac

CamTwist for Mac is a free video app that allows you to spice up your chats with all sorts of original and special effects. It can be a little complex to set up, but once installed, it works with most video chat services such as Skype, Yahoo! Messenger, and uStream. You can also stream from the desktop or Flickr.

CamTwist includes a Studio section which allows you to do live mixing, such as adding overlays, switching cameras, or creating a live slideshow. The more technically gifted users can also create their own special effects. With over 50 effects available by default, you can get really creative without spending a single cent. Additionally, CamTwist offers AppleScript support, opening up the application to customization.

Despite the initial complexity, CamTwist is a very good free tool to add fun effects to your video chats.